1. Lacking brilliance or vitality
   "a dull lacklustre life"
   - lackluster [US], lusterless [N. Amer], lustreless [Brit, Cdn] 
2. Lacking lustre or shine
   "staring with lacklustre eyes"
   - lackluster [US], lusterless [N. Amer], lustreless [Brit, Cdn]

See also: dull, hebetudinous

• radio radiation
• radio receiver
• radio reflector
• radio set
• radio signal
• radio source
• radio spectrum
• radio station
• radio telescope
• radio transmitter
• radio wave
• radio-controlled
• radio-controlled aircraft
• radio-frequency spectrum
• radio-gramophone
• radio-opacity
• radio-opaque
• radio-phonograph
• radioactive
• radioactive dating
• radioactive decay
• radioactive dust
• radioactive iodine excretion test
• radioactive iodine test
• radioactive iodine uptake test